Today Rebecca is 34 years old

boomgoesthegmat wrote:Today Rebecca, who is 34 years old, and her daughter, who is 8 years old, celebrate their birthdays. How many years will pass before Rebecca’s age is twice her daughter’s age?
A) 10
B) 14
C) 18
D) 22
E) 26

Answer: C

I think the best (i.e., fastest) approach is to TEST the answer choices.
However, for those who prefer using algebra, here's an algebraic approach:

Let x be the number of years from today.
So, x years in the future, Rebecca's age will be 34 + x
And, x years in the future, her daughter's age will be 8 + x

We want Rebecca’s future age to be twice her daughter’s future age.
We can create the following "word equation": (Rebecca’s future age) = 2(daughter’s future age)
Or we can write: (34 + x) = 2(8 + x)
Expand to get: 34 + x = 16 + 2x
Solve to get: x = 18

Answer: C

Cheers,
Brent

Hi boomgoesthegmat,

Certain questions in the Quant section can be solved rather easily by TESTing THE ANSWERS.

Here, we know that Rebecca's current age is 34 and her daughter's age is 8. We're asked how many years will need to pass by before Rebecca's age is exactly TWICE her daughter's age. Since the 5 answer choices are all numbers, we can TEST them until we find the match...

A) 10 years
Rebecca will be 44
Daughter will be 18
44 is NOT double 18

B) 14 years
Rebecca will be 48
Daughter will be 22
48 is NOT double 22

C) 18 years
Rebecca will be 52
Daughter will be 26
52 IS double 26
This must be the answer.

Final Answer: C

GMAT assassins aren't born, they're made,
Rich

boomgoesthegmat wrote:Today Rebecca, who is 34 years old, and her daughter, who is 8 years old, celebrate their birthdays. How many years will pass before Rebecca’s age is twice her daughter’s age?
A) 10
B) 14
C) 18
D) 22
E) 26

We are given that Rebecca is 34 and her daughter is 8. We can let n = the number of years before Rebecca is twice as old as her daughter. At that time, Rebecca will be (34 + n) years old and her daughter will be (8 + n) years old, and Rebecca will be twice her daughter’s age:

34 + n = 2(8 + n)

34 + n = 16 + 2n

18 = n

Answer: C